1. Field of the Invention
The present invention relates to a vehicle motion control device for preventing a roll angle of a vehicle from being excessive.
2. Description of the Prior Arts
There has conventionally been a demand for controlling a vehicle motion so as to prevent the running state of the vehicle from being unstable due to the occurrence of an excessive roll angle (an inclination angle in a roll direction from a horizontal direction of the vehicle body in this specification) on the vehicle. This roll angle depends upon the magnitude of an actual lateral acceleration that is a component of an acceleration actually exerted on the vehicle in the side-to-side direction of the vehicle body based upon centrifugal force exerted on the vehicle when the vehicle is in the turning state, and increases with the increase of the actual lateral acceleration. On the other hand, the magnitude of the actual lateral acceleration exerted on the vehicle is decreased by producing a yawing moment in the direction opposite to the turning direction of the vehicle or by decelerating the vehicle.
From the above, a vehicle motion control device disclosed in the patent document 1 has a lateral acceleration sensor for detecting an actual lateral acceleration exerted on the vehicle, wherein, when the vehicle is in a turning state and the actual lateral acceleration detected by the lateral acceleration sensor exceeds a predetermined roll-over preventing threshold value, it judges that there is a tendency of an occurrence of excessive roll angle caused on the vehicle, thereby executing a control for exerting predetermined braking force on the outer wheel in the turning direction of the vehicle. According to this device, a yawing moment is given to the vehicle in the direction opposite to the turning direction of the vehicle due to the predetermined braking force, whereby the magnitude of the actual lateral acceleration exerted on the vehicle is decreased, thereby being capable of preventing the occurrence of the excessive roll angle on the vehicle.
[Patent Document 1]
Japanese Unexamined Patent Application No. HEI10-81215
In general, the lateral acceleration sensor is mounted at a predetermined position of the vehicle body (for example, in the vicinity of the center of gravity of the vehicle) with a predetermined posture. It detects a value of a component of external force exerted on the vehicle in the side-to-side direction to obtain a lateral acceleration caused on the vehicle. Accordingly, in case where there is an error in the mounting orientation and mounting angle of the lateral acceleration sensor to the vehicle body and hence the direction of the lateral acceleration sensor that should be agreed with the side-to-side direction of the vehicle body does not actually agree with the side-to-side direction of the vehicle body, the lateral acceleration sensor cannot accurately detect the value of the component of the external force exerted on the vehicle in the side-to-side direction, with the result that it cannot accurately obtain the lateral acceleration exerted on the vehicle.
However, there inevitably exists an error in the form of the lateral acceleration sensor itself or in the form at the mounting section of the lateral acceleration sensor in the vehicle body, so that an error can inevitably be produced in the mounting orientation or mounting angle of the lateral acceleration sensor to the vehicle body. Accordingly, in the disclosed device, there may be the case where the control for exerting the braking force is not executed when it should be executed since the lateral acceleration is detected somewhat smaller, or the case where the control for exerting the braking force is executed when it should not be executed since the lateral acceleration is detected somewhat greater. In other words, it cannot accurately judge that there is a tendency that excessive roll angle occurs on the vehicle, resulting in that there may be the case where the occurrence of the excessive roll angle cannot suitably be prevented.